Process of smelting



Patented Jan. 18, 1938 UNITED STATES orleE No Drawing. Application March12, 1936, Serial No. 68,444

2 Claims.

My invention relates to the smelting of sulfide ores by the combustionof the oxidizable elements of the ores, thereby producing matte of adesired grade, or metallic copper.

Having in mind the defects of this special class of smelting processesin particular, and the ponderous and complicated character of modernsulfide ore smelting in general due to the use of roasters, blastfurnaces and reverberatory furnaces and heavy and expensive machineryrequired in their operation, an object of my invention is to provide aprocess in which a furnace is operated continuously at a smelting heatthereby eliminating great changes in temperature which is detrimental tofurnace linings.

Another object is to provide a process wherein the sulfide mineral andthe silicious ores are intimately mixed in the charges so that silica isimmediately available to flux iron oxides formed in the process.

Another object is to use to the fullest possible extent the heatproducing elements of ores for ore smelting and concentration.

Another object is to avoid the use of masters, reverberatory furnaces,blast furnaces etc., thereby accomplishing a material economy inequipping the plant and enabling a small operator to smelt his own oreswithout too great an investment in the furnaces.

Another object is to avoid the loss of heat producing elements which areWasted by roasting sulfide ores.

Another object is to avoid the use of great quantities of carbonaceousfuel, thereby effecting a great economy in operation.

A still further object of the invention is to provide a process ofsmelting which is more efficient, simple and economical as compared withother processes.

I attain the above and other objects by carrying out the followingdescribed process:

The sulfide ores, With other ores in mixture, are smelted in a batteryof converter furnaces, maintaining a condition therein whereby aquantity of molten matte is always available in one furnace as a starteror nucleus for another furnace. This nucleus of molten matte is ofsufficient quantity to cover the tuyres and is used for the purpose ofproviding a bath through which compressed air is forced and to whichmixed ores are periodically added in small quantities, the ore beingprovided either naturally or artificially with the required amount ofsilica mixed or incorporated with it.

The term silicious ores as used in this specifi cation refers to suchmaterial as is commonly called silica in copper converter plants, whichconstitutes a flux in which silicon dioxide is the active agent andconsists preferably of high silica quartzite ores of copper, gold, andsilver. The term silica refers to silicon dioxide, SiOz as found in suchminerals as quartz, flint, etc.

The above term small quantities is used to distinguish this process fromany in which ores are added in mass to an empty furnace.

This is essentially a combined pyritic smelting and bessemerizingprocess and may be carried out in a battery of suitable basic linedconverters; in fact this apparatus is the furnace in mind for thepurpose, but any suitable tilting or stationary furnace may be used ifbuilt so as to fulfill the requirements of the process. Ordinarily ablast pressure of from 12 to 20 pounds to the square inch is used.

I have found that the use of a battery of converter furnaces in themanner herein described accomplishes a very material increase inproduction of. metal at a decreased cost as well as providing aconvenient means of obtaining any desired molten product during theprosecution of the process.

It is preferred to use two or more converters or furnaces each of whichwill be operating at different stages of the process at the same time sothat a nucleus of low grade molten matte may be obtained from onefurnace for another furnace which has finished and poured its product,thereby providing a substantially continuous produc tion of matte ormetal and yet permitting the shutting down of any of the converters forrepair or other purposes.

The several furnaces may be of different size or shape. They may operatein a horizontal or vertical position. By furnaces of the converter typeI mean the furnaces are provided with tuyres through which a blast ofcompressed air is injected into a molten bath of aforesaid quantitycontained therein.

The process depends for its success largely upon rapidity of oxidationand the quick removal of the gaseous products of combustion, andtherefore the gas outlets of the furnaces should not be restricted.

It is of course understood that I use air under controlled pressure toblow through the tuyresthrough the molten metal to provide the necessaryoxygen to oxidize the sulfur and iron and thereby to produce thesmelting heat and new compounds.

The process may be used to produce a copperfree iron sulfide matte frompyritic iron ores for the purpose of collecting gold, silver or metalsother than copper. Y

The process may be used to produce a white metal consisting of a mixtureof copper and nickel sulfides since nickel-copper alloys follow, in thematte blow, exactly the same laws as govern copper alone.

The process may be .used' to produce metallic copper .by blowing acopper sulfidewhite metal produced from copper matte, and further, theprocess may be used to smelt limited quantitiesof oxide, carbonate andother ores together with the sulfide ores. The fact that I useasiliciousfiux permits the use of silicious ores having considerablemetallic value. I

For the production of an iron'sulfidematteithe following typical chargeis suggested and-may be made up of the following elements inthefollowing approximate proportions. Silica 25%, alumina 5% ,jlI0I1 35%,sulfur'35%. The proportion of silica may be'somewhat'increased with freesilica ores. For the production of copper sulfide matte thefollowingapproximate charge is suggestedrsilica 29%, alumina 5%, iron35%, sulfur 35% and copper 5%. For the production of a copper-nickelmatte'theichargeis similar to the copper-sulfide matte except thechargeof the copper and nickel together should approximate at least 5% for aclose collectionofthe .gold and silver of the ores.

These charges may be varied to suit the conditions but it will be foundthat the process allows of higher silica slags and thus .a, good metal.I provide, .byany known process a quantity of molten sulfides as anucleus for aseries of steps in smelting; for instance this nucleus maybe originally provided by heating afurnace or converter until the brickor other. lining has become red,.or even white hot, then introducing acomparatively small amount of cokeorcth'er fuel, say about two hundred,pounds, then placing a certain tonnage of ,ore, say"-l5 tons, on top ofthe fuel and turning on. a slight blast of compressed air of about oneor two pounds persquareflinchuntil aquantity of sulfidesis smeltedout-of the ore and is.in sufficient quantity to cover the tuyres.

The blast is then gradually increaseduntil the charge has nearedthepoint ofbeing entirely smelted when a'blast of from twelve to twentypounds is used until thecharge is fully. fused, and may now be used as anucleus for the production of matte. V

A nucleus of matte havingbeen obtained as above described/insufiicient'quantityto cover the tuyres and provide a molten bath,.smallquantities of a mixture of sulfide. mineral and silicious .ores areadded'from time to time to this bath and .are smelted by the heatproduced by the oxidation of theiron and sulfur of the mattebath. "Thesmelted ores increase the volume of the matte. The silicious ores fluxand slag the iron oxideand the resultant slag is poured periodically.The

.quantity of the'matte is'thus built upto the capacity of the furnace.The quality of the matte is enriched by the oxidation of the ironsulfide by the blast and the slagging of the iron oxidewith silica.

When. a sufiicientgquantity of matte has been accumulated a portion maybe transferred to a smelting continued in the first furnaceby theaddition of fresh ores. The nucleus should be transferred to the hotempty furnace in the earlier stages of the converting so as to provide anucleus of low grade matte therefor, or a quantity of such low gradematte may be set aside in a suitable container until needed as a moltennucleus for any hot empty furnace.

The steps in the process are normally as follows:

l. The furnace having been in use is still hot,

or in the case of a first charge the furnace is suit ably heated.

2. A sufficient quantity of molten matte nucleus 'is placed in thefurnace to cover the air inject- :ing means.

3. A mixture of sulfide and silicious ores is aiddedgin small quantity,until enough has been added for one blow for matte and slag production.

4. The chargingof the ores is discontinued and *sdfiiizient' blowingtimeallowed to sufficiently fuse the ores so thata" fluid slag may beobtained and the temperatureof the furnace raised.

5. Slag is poured from the furnace.

' fig-The chargingof ore, blowing and slagging as in steps 3, 4-a-n'd 5is repeated untila sufficient volume of matte is accumulated to transfera part thereof asa nucleusand still -leave sufficient matte in thefurnace for a-nucleus to repeat the aforesaidsteps.

"7.'-The abovequa-ntity of molten matte, as in step No; 2 is removed'tostart operation in another furnace, or this portion may be'added' to'another furnace already =in process of operation.

8. The steps 3,-4 and 5 of the process-are then continued as beforeandthe concentration of -'t-he=-matte-results from such continuation bythe elimination'of theironsulfide-throug-h the oxidizinge'ffect ofthejairblastpassing through the matte, and slagging iron oxide withthe'silica ofthebharge until a concentrated iron matte, a copper sulfidewhite metalor a nickel-copper sulfide white metal is-obtained=as thecase may 'be. In the case of -aconcentrated iron sulfide matte or anickel-copper white metal, these are the ultimate products of theprocess. They are then poured and'the process repeated.

9.-In the case of having produced a copper sulfide white metal thisWhite metal is finished to metallic copper byan oxidizing blow, thecopper poured-and the process repeated.

Silica may be furnished by the gangue rock of the sulfide ore. Otherwisesulfide and silicio us' ores are charged, in intimate mixture so thatsilica may be immediately available, when the iron oxide isiformed,to'slag this oxide and to prevent '-the excessive formation of thehigher oxides of iron as would be the case in the'absence of sufficientsilica.

The amount of'the ore charged for any particular period of smeltingand'blowing for slag depends upon-the character of-the ore; ordinarilyfive or six-repeated charging, blowing and skimmingperiods will benecessary for the accumulation of 'afull charge, the idea being to skimoften enoughto relieve the furnace of burdensome quantities of slagwhichis an inert mate rial. The ore. is charged through the stack while.the furnace istilted forward .and.the air partially shutoff, or..it ischarged .by means of a Garragun orother contrivance while the furnace isblowing withfull' blast butnot in such quantities as to solidify themolten material therein. For instance, normallyv a .completeblow "forslag will require about an' hour. Ordinarily the charge of ore can beput in at one time at the earlier part of the blow, but it can readilybe seen that in the case of having a small nucleus of molten material itmay be advantageous to add the charge of ores in two or more separateand distinct parts, each charging requiring several minutes. But in anycase the charging of all ore should be discontinued for say 20 minutesor more before the skimming of slag is attempted, during which time theair supply is continued in order to allow for the smelting of the oreand to allow the contents of the converter to heat up to a sufiicientdegree, such that magnetic iron oxide may be reduced and a clear fluidslag formed.

I have found that the proposal of previous inventors as to thecontinuous charging of ore through the whole blow is not desirable forthe following reasons: In a strongly oxidizing operation, such as iscarried on in a bessemer converter, the higher oxides of iron willeasily be formed.

The formation of these higher oxides occurs most readily when thefurnace is slightly cooled by the introduction of fresh ores, thereforesuch charge must have a plentiful supply of silica to reduce thequantity of such higher oxides thus formed. The temperature of thefurnace is rapidly raised by the above described oxidizing reactions,thereby quickly reducing such higher oxides of iron as may have beenformed.

The importance of preventing the formation if possible, of magneticoxide of iron, or if formed to reduce it, may be understood from thefollowing facts:

First, these oxides freeze at the tuyeres and colder parts of theconverter thus making it exceedingly difiicult to keep the tuyres openso as to get the blast into the furnace.

Second, the slag does not readily separate.

Third, the slag has a mottled appearance on the skimming rabbleindicating that metal is being carried into the slag and the flow ofslag stops short in the pouring thus preventing a clean skim.

In a process of this special class using little, if any, carbonaceousfuel, the conditions recited above must especially be guarded against asa precaution to preserve the heat of the furnace and proper workingconditions. However, with proper practice, i. e., that of using mixedores and segregating the charging of the ores to the earlier part of theblow, the heat developed is suificient and the working conditions andthe results are satisfactory.

The process may be carried out in a single furnace by setting aside aquantity of matte in a suitable container and reserving it in its moltencondition until needed as a nucleus to repeat the process.

In the case that a withdrawal of matte is not needed from any particularcharge the matte may be built up as to quantity and quality withoutseparating any matte and the ultimate product obtained.

In the practice of the invention it may be found advantageous to operatefor a time one furnace of the battery solely in the stage of smeltingand matte accumulation, upon anucleus of molten matte; making transfersto other furnaces of the battery as a surplus, above the requirednucleus, is accumulated. This furnace will continue in matte production,always retaining and building up from a nucleus of molten matte. Anotherfurnace of the battery being used to accumulate a full charge of whitemetal and blow this to metallic copper.

In the above description it is not intended to imply that the severalores must be premixed before charging, though normally such would bepreferred, but the required quantities of the several ores can be dumpedeither together or at practically the same time (without sufiicientinterval to permit independent action,) into the converter where theactual mixing of the ores is caused by the agitation of the molten masstherein.

Having fully described the invention, what I claim as new and desire tosecure by Letters Patent, is:

1. A process of producing matte, white metal and copper which comprisesthe steps of periodically charging small amounts of a mixture of sulfideore and silicious fiux in amounts sufiicient to flux the iron oxideformed in converting the sulfide ore upon a nucleus of molten matte in acontainer provided with means for injecting air into the chargecontained therein, the matte being sufiicient to cover the air injectingmeans; blowing air into the mass, whereby the mixture of sulfide ore andsilicious flux is periodically smelted by the heat generated from theoxidation of the iron and sulphur by means of the air blast injectedinto the matte until a desired quantity of matte is obtained; separatinga portion of this matte, as a nucleus, and maintaining it in its moltencondition; and continuing the smelting process to restore the quantityof matte in the said container and simultaneously building up the gradeof the matte, until the quality of the matte reaches the white metalstage; converting the white metal to copper by means of an air blastinjected therein; pouring the copper; and introducing into the hotconverter the previously separated portion of molten matte as a nucleusfor a repetition of the process.

2. A process of smelting sulfide ore which comprises periodicallyintroducing a charge consisting of small amounts of a mixture of sulfideore and silicious flux, the fiux being sufiicient in amount to slag theiron oxide formed in converting the sulfide ore until enough has beenintroduced for one blow for matte and slag production; the charge beingintroduced upon a nucleus of molten matte in a container provided withmeans for injecting air into the charge con tained therein, the mattebeing sufiicient in amount to cover the air injecting means;periodically smelting the mixture of sulfide ore and silicious fiux bythe heat generated from the oxidation of iron and sulfur by means of anair blast injected into the matte, without further additions of ore orflux during the smelting period in order to maintain the full heat ofthe blow throughout each smelting period; repeating the periodiccharging and smelting of a mixture of sulfide ore and silicious fluxuntil the desired quantity of matte is obtained; separating a portion ofthis matte, maintaining it in its molten condition; and using the sameas a nucleus in repeating the above sequence of operations.

FORREST E. WING.

